Axonal degeneration often precedes the death of neuronal cell bodies in neurodegenerative diseases, thus inhibiting axonal degeneration represents a potential novel point of intervention in combating these diseases. Axonal degeneration is now regarded as an active, self-destructive program in which the ubiquitin proteosome pathway plays an important role. We have identified a novel E3 ubiquitin ligase, ZNRF1 that is induced in Schwann cells after nerve injury. ZNRF1 is also specifically upregulated in neurons, along with ubiquitin, after axonal damage. ZNRF1 and another related E3 ligase, ZNRF2, are both highly expressed throughout the nervous system during development and in adulthood. Using in vitro assays we have found that ZNRF protein activity is required for normal axonal degeneration. In this proposal, we have outlined experiments to define how ZNRF proteins influence axonal degeneration. First, we will analyze the phenotypes of ZNRF-deficient mice in order to determine physiological roles of these proteins. In particular, the will focus our analysis on the processes of nerve degeneration/regeneration after mechanical and metabolic injury as well as synaptogenesis. We also aim to identify proteins targeted by ZNRF-mediated ubiquitination. A proteomic analysis will be performed to identify ZNRF targets either from brain tissues of mice deficient for ZNRF proteins or from affinity-purified complex containing dominant negative ZNRF mutants and ZNRF targets. These studies will improve our understanding of axonopathy and neuronal degeneration, and provide a basis for developing novel treatments for neurodegenerative diseases [unreadable] [unreadable]